This invention relates to apparatus and methods for molding aggregate blocks.
Apparatus for the mechanized molding of concrete blocks are well known, as exemplified by U.S. Pat. No. 3,679,340, the disclosure of which is incorporated herein by reference. Briefly, the molding of standard building blocks involves the introduction of moldable block material into a mold box or sleeve having fixed, straight-sided cavity walls that extend longitudinally between open top and bottom ends of the mold. A pallet is positioned to close the bottom of the cavity and a top plate, or template, overlies the top of the mold, and is formed with an opening aligned with the cavity to receive moldable block material into the cavity. The material is charged into the mold from a feed box which is moved from the side into position over the mold and discharges material through a bottom chute, after which it is returned clear of the mold. A stripper head is lowered from above into the cavity to close the top of the mold and engage the top of the material. With the cavity closed, the mold box assembly is vibrated which, together with the weight of the stripper head, serves to compact and shape the material into the form of a block. The completed block is vertically stripped through the bottom of the mold by lowering the pallet and stripper head together, and then is conveyed onward on the pallet for further processing. The stripper head is returned and a new pallet positioned against the bottom of the cavity to ready the mold for the next cycle.
It will be appreciated that the laterally immovable cavity walls restrict the type of block that can be produced in the mold to ones having straight-sided walls or side contours that extend in the longitudinal direction of stripping. Lateral undercuts or projections are not permitted, as such would interlock the block and cavity walls in the longitudinal direction, preventing stripping.
FIGS. 2 and 3 illustrate a complex block having such lateral undercuts and projections. A mold box whose parts split laterally has been employed to form such blocks, the mold parts having the appropriate projecting and recessed mold surfaces to impart the corresponding shape to the block. The mold parts are initially inwardly displaced to provide a laterally contoured mold cavity open at its longitudinally opposite top and bottom ends. The bottom of the mold is closed by a pallet, and a top plate overlies the top of the mold and has an opening therein aligned with the open top of the mold. A feed box is moved laterally into position over the mold between the top plate and the underside of an upper stripper head to deliver the block material into the mold cavity through a bottom shoot, after which the feed box is returned clear of the mold and stripper head.
As the feed box moves into and out of position, a wire brush carried along the top of the feed box sweeps across the underside of the stripper head to remove any block material that may have accumulated from the previous mold cycle. For this particular block, the underside of the stripper head is heavily contoured. Large depending features extend into the mold and help form the projecting side features of the block as well as shaping the top surface of the block during molding.
Following compaction of the block material within the cavity, the mold parts are laterally split and retracted beneath the top plate sufficiently to disengage the mold surface clear of the block, to permit subsequent longitudinal stripping of the completed block through the bottom of the mold through conjoint downward movement of the platform and stripper head.
Some difficulties have been encountered in forming such blocks having laterally extending side features using split mold tooling of the type described above. The block material tends to accumulate on the upper surfaces of the projecting portions of the mold tooling, particularly in the inside corner regions. The material must manually swept or blown from these regions between mold cycles, slowing the process and requiring the attendance of an operator. The block material also tends to accumulate on the underside surface of the stripper head. The traditional wire brush carried on the feed box is unable to reach the deep inside corner features where the material is most prone to accumulate. Further, those bristles that sweep across the large projecting features of the stripper head quickly fatigue and break off.
Apparatus for molding blocks having such laterally extending side contours includes the provision of a mold having a mold cavity that is open at the top and bottom thereof and a top plate overlying the mold formed with an opening aligned with the open top of the cavity for accommodating the charge of moldable block material into the mold. A bottom pallet is supported for movement into operative engagement with the bottom of the mold for closing the bottom of the cavity. A stripper head is supported above the mold for movement into the cavity through the open top to engage and shape the top of the material in the mold.
The mold includes at least one retractable liner member having an inner shape-imparting surface supported for engagement with a side of the block material during molding when in a first use position. The liner member is laterally movable out of engagement with the block material to a retracted position beneath the top plate for releasing the molded block material.
The shape-imparting surface of the liner member has at least one problem area that is susceptible to the accumulation of the moldable block material between mold cycles. According to the invention, the top plate includes a mold clean-out system having at least one fluid outlet in the top plate positioned to communicate with the problem area of the liner member surface when the liner member is in the retracted position. The cleanout system is operative to direct a flow of pressurized fluid such as air through the outlet and on to the problem area for removing any such accumulation of block material therefrom.
The invention has the advantage of incorporating the clean-out system in the top plate of the mold assembly with outlets strategically positioned for directing pressurized air onto the problem areas of the mold when in the retracted position between mold cycles. The clean-out system thus automates the cleaning of the molds without interruption of the molding process and without requiring the assistance of an operator.
According to another aspect of the invention, the air clean-out system includes an air knife mounted to the feed box having an air outlet positioned to direct a flow of high pressure air against the underside of the stripper head to remove any accumulated block material thereon. The air knife has the advantage of being able to remove accumulated material from all areas of the stripper head underside, including the deep inside corner regions where the traditional brush cannot reach. The air knife further avoids the problem of bristle damage associated with sweeping across largely projecting features of a stripper head underside.